SOUTH SAN FRANCISCO, Calif., July 9 /PRNewswire-FirstCall/ --
Rigel Pharmaceuticals, Inc. (NASDAQ:RIGL)
today announced that R788 (fostamatinib disodium) produced
significant clinical improvement in rheumatoid arthritis (RA)
patients in the recently completed TASKi2 Phase 2b clinical trial
of 457 patients treated for up to 6 months. The groups treated with
100 mg of R788 bid (twice a day) and 150 mg qd (once a day)
reported higher ACR 20, ACR 50, ACR 70 and DAS28 response rates
than the placebo group. The efficacy results for the two dosing
groups were comparable, although the response rates for the 100 mg
bid group was uniformly greater. Consistent with the previous Phase
2a clinical trial (TASKi1), the onset of effect of R788 occurred
within one week after the initiation of therapy and was maintained.
The most frequent adverse events were expected based on TASKi1 and
appear to be manageable. The significant, early and sustained
efficacy, combined with a good safety profile, supports Rigel's
plans to conduct corporate partnership discussions with respect to
R788 and initiate a Phase 3 clinical program with R788 in RA in the
first half of 2010 with a corporate partner.

"These are impressive results," said James M. Gower, chairman
and chief executive officer of Rigel. "The data from this clinical
trial and the soon to be completed TASKi3 clinical trial, a total
of over 670 patients, will guide the design of the Phase 3 trials
that we plan to launch with a corporate partner in the first half
of next year, " he added.

Efficacy Results
Treatment N of Pts ACR 20 ACR 50 ACR 70 DAS28<2.6
Placebo 153 53 (35%) 29 (19%) 16 (10%) 9 (6%)
150 mg qd 152 87 (57%) 49 (32%) 21 (14%) 26 (17%)
p<0.001 p=0.007 p=0.34 p=0.003
100 mg bid 152 101 (66%) 65 (43%) 43 (28%) 41 (27%)
p<0.001 p<0.001 p<0.001 <0.001
p values compared to placebo
Note: At 6 months. All patients were on stable doses of methotrexate
throughout the clinical trial.
* The results presented are based on an intention to treat analysis that
includes all randomized patients, regardless of how long treatment
lasted. Any patient who dropped out of the study for any reason,
or for whom month 6 data were unavailable, was considered a treatment
failure (ACR non-responder). Disease Activity Scores are based on a 28
joint count and CRP or an ESR at week 24 (depending on which was the
qualifying biomarker).
Safety Results

The most common clinically meaningful drug-related adverse
events noted in TASKi2 were diarrhea and hypertension. Dose
reduction options were pre-specified in the trial protocol and in
cases where doses were reduced, patients generally completed the
clinical trial with minimal safety issues. The most common adverse
events in the trial overall were related to infections, though
these were generally evenly distributed among the placebo and
active dose groups.

The mean increase in blood pressure from baseline at 6 months,
using a last observation carry forward methodology, was less than
0.5 mmHg for the 150 mg qd dose group and approximately 1 mmHg for
the 100 mg bid dose group. Approximately 18% and 23% of patients in
the 150 mg qd and the 100 mg bid dose groups, respectively, had
blood pressure medication adjusted or in some cases initiated
during the course of the study, compared with 7% of the placebo
patients. The blood pressure was successfully reduced in these
patients, and their blood pressure was generally well controlled
throughout the trial. The blood pressure medications were standard
doses of common blood pressure medications such as ACE inhibitors
or diuretics.

"R788 continues to perform with strong efficacy and good
tolerability in the groups of patients with RA who have failed to
respond to methotrexate," said Elliott Grossbard, M.D., chief
medical officer for Rigel. "We now have a much better understanding
of R788's safety profile and believe that the observed side effects
may be effectively managed," he added.

TASKi2 was a 6 month, multi-center, randomized, double blind,
placebo controlled, parallel dose clinical trial involving 457 RA
patients in the U.S., Latin America and Europe who had failed to
respond to methotrexate alone. The patients were randomly assigned
to two cohorts and thus received R788 orally in either 100 mg bid
(twice daily) or 150 mg qd (once daily) doses or placebo for a
period of 6 months. Within in each cohort, patients were assigned
on a 2:1 basis to R788 or placebo. All of the patients continued to
receive their same stable dose of methotrexate throughout the
clinical trial period.

Efficacy assessments for each participant were based on the
American College of Rheumatology criteria, which denotes at least a
20% (ACR 20) improvement, at least a 50% (ACR 50) improvement, or
at least a 70% (ACR 70) improvement, from the baseline assessment
at the end of the 6 month treatment period. The ACR measurement
factors include reported physician and patient global assessment of
disease activity, patient reported pain score, and any change in
C-reactive protein (CRP) in the patients' blood. The primary
efficacy endpoint for the study was the percent of patients
assigned to the R788 100 mg bid dose who were ACR 20 responders at
the end of 6 months. Secondary efficacy endpoints included a
comparison of response rates for the R788 100 mg bid and R788 150
mg qd doses at the ACR 20, ACR 50 and ACR 70 scores, as well as
Disease Activity Scores (DAS) over the period of 6 months.

R788 and RA

RA is a progressive, painful and potentially debilitating
disease, that affects more than 2 million people in the U.S. It is
a chronic inflammatory disease that puts the body's immune system
into overdrive where it ultimately causes inflammation in the
joints and destroys soft tissues, cartilage and bone. Rigel's R788
is a novel, orally available syk kinase inhibitor designed to
interrupt the cellular signaling at the trigger point of
inflammation, thereby stopping the progression of the disease.

Conference Call and Webcast Information

Rigel will host a conference call to discuss the R788 TASKi2
Phase 2b clinical trial of R788 in rheumatoid arthritis, the
Company's plans for further development and related matters today,
July 9, 2009, at 8:00am EDT/5:00am PDT. A presentation related to
the TASKi2 trial results is available on Rigel's website homepage
at http://www.rigel.com/. To access the
live call, please dial 866-543-6408 (domestic) or 617-213-8899
(international) 10 minutes prior to the start time and use the
passcode 40038100. A replay of the call will be available at
approximately 11:30am EDT/8:30am PDT on July 9, 2009 until July 16,
2009. To access the replay, please dial 888-286-8010 (domestic) or
617-801-6888 (international) and use the passcode 48864759. The
conference call will also be webcast live and can be accessed from
Rigel's website at http://www.rigel.com/. Please
connect to Rigel's website several minutes prior to the start of
the live webcast to ensure adequate time for any software downloads
that may be necessary. Further information on R788 in RA is
available at Rigel's website: http://www.rigel.com/rigel/rheumatoid_arthritis.

About Rigel (www.Rigel.com)

Rigel is a clinical-stage drug development company that
discovers and develops novel, small molecule drugs for the
treatment of inflammatory/autoimmune diseases and metabolic
diseases. Our pioneering research focuses on intracellular
signaling pathways and related targets that are critical to disease
mechanisms. Rigel's productivity has resulted in strategic
collaborations with large pharmaceutical partners to develop and
market our product candidates. Rigel has product development
programs in inflammatory/autoimmune diseases such as rheumatoid
arthritis, thrombocytopenia and asthma, as well as in cancer.

This press release contains "forward-looking" statements,
including statements related to the potential efficacy and
commercial potential of R788 and Rigel's plans to pursue further
clinical development thereof and a corporate partnership. Any
statements contained in this press release that are not statements
of historical fact may be deemed to be forward-looking statements.
Words such as "believe," "plan" and similar expressions are
intended to identify these forward-looking statements. There are a
number of important factors that could cause Rigel's results to
differ materially from those indicated by these forward-looking
statements, including risks associated with entering into a
corporate partnership agreement and reliance on a corporate
partner, the timing and success of clinical trials and the
commercialization of product candidates, potential problems that
may arise in the clinical testing and approval process and Rigel's
need for additional capital, as well as other risks detailed from
time to time in Rigel's SEC reports, including its Form 10-Q for
the quarter ended March 31, 2009. Rigel does not undertake any
obligation to update forward-looking statements.